O'Gara joined centre Rua Tipoki in leaving the field in the first-half of the Magners League game at Thomond Park, although unlike Tipoki, he is expected back in action with a fortnight.
"Ronan's injury is not as serious as first thought and, although doubtful for the trip to Wales next week, he is expected to be fit in time for the visit of Sale Sharks," said a Munster spokesman.
O'Gara became the first player to reach 1,000 points in the Heineken Cup before Christmas and is hoping to guide the cup holders through to the last eight over the final two Pool rounds this month.
A double Lion, O'Gara is also one of the lynchpins in Ireland's Six Nations plans and is bound to figure in Ian McGeechan's thinking when the 2009 British & Irish Lions head coach names his squad for South Africa.